Optical source driver circuit having overshoot controller

Abstract

A driver circuit configured to generate a drive signal for an optical source comprises an overshoot controller that provides an amount of overshoot for a given logic state of the drive signal as a function of a duration of at least one previous logic state of the drive signal. The drive signal may alternate between a first logic state associated with a first operating mode of the optical source and a second logic state associated with a second operating mode of the optical source. The overshoot controller may be configured to provide amounts of overshoot for respective instances of the first logic state that are proportional to the durations of their respective immediately preceding second logic states. The driver circuit may be implemented in a heat-assisted magnetic recording system in which the optical source alternates between on and off states associated with respective magnetic write and magnetic read modes.

What is claimed is: 
     
       1. An apparatus comprising:
 a driver circuit configured to generate a drive signal for application to an optical source; 
 the driver circuit comprising an overshoot controller operative to provide an amount of overshoot for a given logic state of the drive signal as a function of a duration of at least one previous logic state of the drive signal. 
 
     
     
       2. The apparatus of  claim 1  wherein the drive signal alternates between a first logic state associated with a first operating mode of the optical source and a second logic state associated with a second operating mode of the optical source. 
     
     
       3. The apparatus of  claim 2  wherein the overshoot controller is configured to provide amounts of overshoot for respective instances of the first logic state that are proportional to the durations of their respective immediately preceding second logic states, such that one of the instances of the first logic state having an immediately preceding second logic state of relatively short duration is provided with a relatively small amount of overshoot and another one of the instances of the first logic state having an immediately preceding second logic state of relatively long duration is provided with a relatively large amount of overshoot. 
     
     
       4. The apparatus of  claim 2  wherein the overshoot controller comprises:
 a charging path through which a capacitive element charges; 
 a discharging path through which the capacitive element discharges; and 
 switching circuitry for controlling activation of the charging and discharging paths responsive to the operating modes of the optical source; 
 wherein the amount of overshoot provided for a given instance of the first logic state, in conjunction with discharge of the capacitive element through the discharging path, is a function of an amount of time for which the capacitive element charges through the charging path during the immediately preceding second logic state. 
 
     
     
       5. The apparatus of  claim 4  wherein the overshoot controller further comprises level-setting circuitry configured to establish a voltage level to which the capacitive element discharges via the discharging path during the given instance of the first logic level. 
     
     
       6. The apparatus of  claim 2  wherein the first operating mode comprises an on state of the optical source and the second operating mode comprises an off state of the optical source. 
     
     
       7. The apparatus of  claim 2  wherein the first operating mode comprises a write mode of the optical source and the second operating mode comprises a read mode of the optical source. 
     
     
       8. The apparatus of  claim 1  wherein the driver circuit comprises a laser driver circuit. 
     
     
       9. The apparatus of  claim 1  wherein the optical source comprises a laser diode. 
     
     
       10. A disk-based data storage system comprising the apparatus of  claim 1 . 
     
     
       11. The disk-based data storage system of  claim 10  wherein the system comprises an optical disk system configured for at least one of recording and playback of data on an optical disk. 
     
     
       12. The disk-based storage system of  claim 10  wherein the system comprises a heat-assisted magnetic recording system configured for recording of data on a magnetic disk. 
     
     
       13. An optical communication system comprising the apparatus of  claim 1 . 
     
     
       14. A method comprising:
 generating a drive signal for application to an optical source; and 
 providing an amount of overshoot for a given logic state of the drive signal as a function of a duration of at least one previous logic state of the drive signal. 
 
     
     
       15. The method of  claim 14  wherein the generating step comprises generating a drive signal that alternates between a first logic state associated with a first operating mode of the optical source and a second logic state associated with a second operating mode of the optical source. 
     
     
       16. The method of  claim 15  wherein the providing step comprises providing amounts of overshoot for respective instances of the first logic state that are proportional to the durations of their respective immediately preceding second logic states, such that one of the instances of the first logic state having an immediately preceding second logic state of relatively short duration is provided with a relatively small amount of overshoot and another one of the instances of the first logic state having an immediately preceding second logic state of relatively long duration is provided with a relatively large amount of overshoot. 
     
     
       17. The method of  claim 15  wherein the providing step comprises providing an amount of overshoot for a given instance of the first logic state, in conjunction with discharge of a capacitive element through a discharging path, that is a function of an amount of time for which the capacitive element charges through a charging path during the immediately preceding second logic state. 
     
     
       18. The method of  claim 17  further including the step of establishing a voltage level to which the capacitive element discharges via the discharging path during the given instance of the first logic state. 
     
     
       19. A computer-readable storage medium having embodied therein executable code for controlling performance of the steps of the method of  claim 14 . 
     
     
       20. An apparatus comprising:
 an integrated circuit comprising at least one driver circuit configured to generate a drive signal for application to an optical source; 
 the driver circuit comprising an overshoot controller operative to provide an amount of overshoot for a given logic state of the drive signal as a function of a duration of at least one previous logic state of the drive signal.